Last updated: · Published by Eternal Elixir
Edited by Elaine Fletcher, Researcher
One 500 mg capsule of Ca-AKG carries roughly 90 to 110 mg of calcium, about a tenth of what most adults need in a day. That number explains most of what is known about Ca-AKG side effects, because the compound itself has very little human safety data and the calcium has a great deal.
Short answer: No completed placebo-controlled trial of Ca-AKG alone has reported side effects in people yet. A 2020 mouse study found no significant adverse effects. The cautions that matter in practice come from the calcium it carries and from a different compound, AAKG, that is often confused with it.
Ca-AKG is calcium alpha-ketoglutarate, the calcium salt of a metabolite your cells make as part of the citric acid cycle. Eternal Elixir sells Ca-AKG 500mg, so we would rather you know the limits of the safety evidence before you order. For what Ca-AKG may support and how strong each benefit claim is, read our Ca-AKG benefits evidence review first. This guide sticks to safety.
Key takeaways
- Ca-AKG side effects in people are poorly documented: the main placebo-controlled trial (ABLE, 1 g a day for 6 months) has not published its results.
- The calcium is the part to count. One capsule adds roughly 90 to 110 mg, two capsules roughly 180 to 220 mg, well under the 2,000 to 2,500 mg daily upper limit for adults.
- Check with a doctor first if you are pregnant or breastfeeding, have kidney problems or kidney stones, have been told to limit calcium, or take levothyroxine, a quinolone antibiotic, dolutegravir or lithium.
Ca-AKG side effects: what the research actually reports
The honest summary is short. Ca-AKG has been tested for lifespan in mice, for bone markers in one small human trial, and for biological age in a retrospective look at customers of one product. None of these studies was designed to catalog side effects in healthy adults.
The mouse lifespan study
The study that started the longevity interest fed middle-aged mice a diet containing 2% Ca-AKG by weight from 18 months of age. Research published in Cell Metabolism reported a longer, healthier life with lower levels of inflammatory signaling molecules. On safety, the authors wrote that they observed no significant adverse effects.
Cataracts and corneal opacity were more common in the treated animals, though neither difference reached statistical significance. Mice are a long way from people, so treat this as a reassuring early signal and nothing more.
The osteopenia trial in postmenopausal women
A six-month, double-blind trial in Poland randomized 76 postmenopausal women with osteopenia to 6 g of AKG as its calcium salt (with 1.68 g of calcium) or to calcium alone. The trial, published in the International Journal for Vitamin and Nutrition Research, found that a marker of bone breakdown fell by 37% in the AKG group by week 24.
Its abstract reports bone results and does not list safety problems. The mouse study authors later cited it as an example of AKG used in human studies without associated adverse effects. That trial used far more AKG each day than one of our capsules supplies.
The biological age reports
A 2021 paper in Aging looked back at 42 people who had taken a product combining Ca-AKG (1 g per dose, timed release) with vitamins for about seven months. Their DNA methylation age dropped by an average of eight years. There was no control group, and one author advised the company that sells the product. The paper says little about side effects.
The proper test is the ABLE trial in Singapore: 120 adults aged 40 to 60, randomized to 1 g a day of sustained-release Ca-AKG or placebo for six months. A 2026 report from that trial put supplement adherence above 90% and overall dropout at 17%. Its side-effect and outcome results had not been published when we checked PubMed in October 2026.
Ca-AKG vs AAKG: side effects that belong to a different supplement
Search for AKG side effects and some of the first results describe emergency room visits. Those reports concern arginine alpha-ketoglutarate (AAKG), the “nitric oxide” ingredient in many pre-workout powders. It pairs AKG with the amino acid arginine instead of calcium.
A case series in Human & Experimental Toxicology described three young men who came to the emergency department with palpitations, dizziness, vomiting, fainting or headache after using AAKG products. The authors suggested the symptoms could reflect blood vessel widening from extra nitric oxide, while noting that other causes could not be ruled out. Ca-AKG supplies no arginine, so those reports do not transfer to it directly. They are still a reason to read the label: some bottles sold as “AKG” contain AAKG or the free acid.
If you are comparing products by form, our Ca-AKG supplement comparison shows how to tell calcium AKG, free-acid AKG and AAKG apart on the ingredient line.
Stocking up on Ca-AKG? Every bottle of Eternal Elixir’s Ca-AKG 500mg carries 60 capsules and ships fast across the United States. Browse the range →
The calcium in Ca-AKG: a dose-by-dose budget
Every Ca-AKG capsule is partly calcium. The Eternal Elixir label lists 500 mg of calcium alpha-ketoglutarate per capsule but gives no separate elemental calcium figure, so we worked it out from the molecular weight. Anhydrous Ca-AKG is about 21.8% calcium, and the dihydrate form is about 18.2%. That gives a range, which is why the table below shows two numbers per row.
The reference points come from the NIH Office of Dietary Supplements calcium fact sheet: an RDA of 1,000 mg a day for adults 19 to 50 (and men 51 to 70), 1,200 mg for women over 50 and everyone over 70, and an upper limit of 2,500 mg a day at ages 19 to 50 and 2,000 mg from age 51. The fact sheet also notes that absorption from supplements is highest at doses of 500 mg or less.
| Daily Ca-AKG amount | Where the dose comes from | Calcium it adds (approx.) | Share of a 1,000 mg RDA |
|---|---|---|---|
| 500 mg (1 capsule) | Eternal Elixir label serving | 91 to 109 mg | About 9% to 11% |
| 1 g (2 capsules) | ABLE trial dose | 182 to 218 mg | About 18% to 22% |
| 6 g of AKG as the calcium salt | Osteopenia trial dose | 1,680 mg (as reported by the trial) | About 168% |
At the label serving, Ca-AKG adds a small share of the day’s calcium. The figure only becomes important when it stacks on top of a calcium supplement, a multivitamin with calcium, fortified foods and a dairy-heavy diet. If you already take 1,200 mg of supplemental calcium, adding Ca-AKG nudges your total closer to the upper limit, and that is worth a conversation with your doctor.
Calcium supplements can cause gas, bloating and constipation in some people, according to the same fact sheet. It also notes that higher intakes of supplemental calcium might increase the risk of kidney stones, although two later systematic reviews found no such link. Those are the Ca-AKG side effects most worth watching for in the first weeks, simply because they are the ones documented for its calcium.
Who should check with a doctor before taking Ca-AKG
Because human safety data are thin, the list below leans on two things: the absence of studies in certain groups, and what is known about calcium. It is a list of reasons to ask first, written for adults who are otherwise healthy.
- Pregnant, trying to conceive or breastfeeding. Ca-AKG has not been studied in pregnancy or nursing. Wait, or ask your obstetric clinician.
- Under 18. No studies in children or teens. Do not give it to them.
- Kidney disease or a history of kidney stones. Your kidneys handle the calcium, and stone formers are often given a calcium plan by their doctor. Follow that plan.
- Told to limit calcium, or high blood calcium. Count Ca-AKG as a calcium source and get advice before adding it.
- Taking prescription medicine. See the interaction list below, and bring the bottle to your pharmacist.
- Already taking a lot of calcium. Add up your supplements and fortified foods first, using the table above.
Medicines that interact with calcium
The NIH fact sheet names four interactions for calcium supplements. Nobody has tested whether Ca-AKG behaves exactly like the calcium forms studied, so spacing the doses is the cautious choice.
| Medicine | What calcium can do | Spacing in the fact sheet |
|---|---|---|
| Levothyroxine (thyroid) | Calcium carbonate can reduce its absorption | Keep 4 hours apart |
| Quinolone antibiotics (for example ciprofloxacin) | Taken together, calcium can reduce antibiotic absorption | Antibiotic 2 hours before or after |
| Dolutegravir (HIV) | Calcium can reduce its absorption | 2 hours before or 6 hours after calcium |
| Lithium | Combined use could raise the risk of high blood calcium | Ask the prescriber before combining |
Interaction questions go well beyond calcium for some supplements. Our guide to what not to mix with resveratrol shows how a polyphenol can raise different issues, which is useful if you take Ca-AKG as part of a wider routine.
How to keep Ca-AKG side effects low if you try it
None of the steps below come from a Ca-AKG trial, because no trial has tested them. They are ordinary supplement habits applied to what is known about this one.
- Start at the label serving. The Eternal Elixir Ca-AKG 500mg label serving is one capsule. At $49.99 for 60 capsules, that works out to about $0.83 per serving. Two capsules match the ABLE milligrams, but not its sustained-release form.
- Take it with a meal. Food tends to make capsules easier on the stomach, and no study has shown a best time of day.
- Add one new supplement at a time. If you also take spermidine or another longevity product, start them a couple of weeks apart. That way you know which one caused any change. Our spermidine benefits and dosage guide covers that compound’s own evidence.
- Keep a two-week note. Write down digestion, sleep and anything new. Stop and ask your doctor if something unexpected shows up.
- Read the label for the form. Look for “calcium alpha-ketoglutarate” on the ingredient line, not arginine AKG.
Ready to try it? You can view Ca-AKG 500mg from Eternal Elixir, which ships across the US with flat $8 shipping or free shipping on orders over $100.
The bottom line
The most reliable thing to say about Ca-AKG side effects today is that the human data are incomplete. The one mouse lifespan study reported no significant adverse effects. The small human studies did not flag safety problems in their abstracts, and the placebo-controlled ABLE trial is the study to watch.
In the meantime, count the calcium, keep it away from the medicines above, and skip it during pregnancy and in childhood. The same evidence-first approach runs through our guide to who should not take TUDCA, if you are weighing other supplements too.
Ca-AKG side effects: frequently asked questions
Who should not take AKG?
Pregnant or breastfeeding women and anyone under 18 should not take AKG supplements without medical advice, because they have not been studied in those groups. People with kidney disease, kidney stones or a calcium restriction should ask a doctor first, since Ca-AKG carries calcium. Anyone on levothyroxine, quinolone antibiotics, dolutegravir or lithium should check the timing with a pharmacist.
What is calcium AKG for?
Calcium AKG is sold as a longevity supplement that may support normal cellular energy metabolism, since alpha-ketoglutarate is part of the citric acid cycle. The interest comes mostly from a 2020 mouse study. Benefits in people have not been established, as the Eternal Elixir product page also states, and the evidence review linked above sorts each claim by its strength.
Can taking calcium supplements have side effects?
Yes. The NIH fact sheet lists gas, bloating and constipation in some people, a possible link between high supplemental calcium and kidney stones, and interactions with several medicines. A single 500 mg Ca-AKG capsule supplies roughly 90 to 110 mg of calcium, a modest amount next to most calcium supplements.
Does Ca-AKG cause constipation?
No study has measured constipation with Ca-AKG specifically. Constipation is a documented effect of calcium supplements, so it is possible, especially if Ca-AKG adds to a high calcium intake. Taking it with food and water, and checking your total calcium, are sensible first steps.
Is it safe to take Ca-AKG every day?
Daily use is how it has been studied: the ABLE trial gives 1 g a day for six months, and the osteopenia trial gave a larger daily dose for six months. Long-term safety in healthy adults is not well documented yet. Follow the label, and ask your doctor if you take medicines or have a health condition.
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Sources
- Asadi Shahmirzadi A, et al. Alpha-Ketoglutarate, an Endogenous Metabolite, Extends Lifespan and Compresses Morbidity in Aging Mice. Cell Metabolism. 2020. PMID 32877690
- Filip RS, et al. Alpha-ketoglutarate decreases serum levels of C-terminal cross-linking telopeptide of type I collagen (CTX) in postmenopausal women with osteopenia: six-month study. International Journal for Vitamin and Nutrition Research. 2007. PMID 17896582
- Demidenko O, et al. Rejuvant, a potential life-extending compound formulation with alpha-ketoglutarate and vitamins, conferred an average 8 year reduction in biological aging. Aging (Albany NY). 2021. PMID 34847066
- Sandalova E, et al. Alpha-ketoglutarate supplementation and BiologicaL agE in middle-aged adults (ABLE): intervention study protocol. GeroScience. 2023. PMID 37217632
- Lu JK, et al. Optimizing accelerometer implementation in a gerotherapeutic trial: feasibility, adherence, and operational insights of ABLE. PLOS Digital Health. 2026. PMID 42789532
- Prosser JM, et al. Adverse effects associated with arginine alpha-ketoglutarate containing supplements. Human & Experimental Toxicology. 2009. PMID 19755457
- NIH Office of Dietary Supplements. Calcium: Fact Sheet for Health Professionals. ods.od.nih.gov
